World time clock

The earth rotates in 24 hours from west to east once on its axis. In this time the sun shines on all regions of the globe one after the other and determines their time of day. To enable a practical calculation of the time, the earth is divided into 24 time zones, which are very simply shown on the map below. Since in a few areas, which belong together, a uniform time has been introduced, the boundaries of the time zones sometimes run along state boundaries. For example, Mexico has Central time. The West European countries including Great Britain has together with the Middle European countries, Middle European time.
According to the map, when it is 13.00 hours there it is only 7 oclock in the morning on the East Coast of the U.S.A. in Japan it is already 21 .00 hours and on the right edge dateline a new day is beginning. The time zones are shown on the world time disk pictured below. Copy or stick this onto a piece of cardboard and cut it out. Colour the panel corresponding to time zone were you live red. Remove the casing and glass from an alarm clock, push the minute hand through the hole in the paper disk and fix it firmly to the hour hand. Make sure that the red coloured panel is exactly over the hour hand. If you rotate the disk with this, it should not stick. The clock will tell you all time of the day on the earth.
Read off first on the red panel the time of the place where you live. If you rotate the disk to the left, you will find the time zones of places west of you. In each panel, the time is an hour earlier. If you rotate to the right, you will find the places east of you. In each panel the time is an hour later. The outer circle continues into the inner circle at the crossed arrows and vice versa. For example in New York it is 6.15 in the morning. Then it is already 20.15 in Tokyo and in New Zealand a new day will begin in 45 minutes. Or in London it is 20.03. What time is it in San Francisco? Look at the world map San Francisco lies in the time zone of Los Angeles. On the rotating disk go to the left to the Los Angeles panel. The time is 11.03.